San Antonio Mayor Castro delivers keynote address Tuesday at DNC

CHARLOTTE, North Carolina (CNN) -- 37-year-old San Antonio Mayor Julian Castro, delivered the keynote address at the Democratic National Convention Tuesday night, September 4th. Castro said he would talk about the American Dream achieved by connecting different generations.

Castro, who was walking outside the convention hall with his brother and friends, said he'll talk about his grandmother coming from Mexico to build a life in the United States, and passing her fortitude down to her daughter, his mother.

The mayor will be the first Latino to keynote at a Democratic convention, organizers have said.

Castro said his speech will be 15 minutes long, and will be laced with what he calls "intergenerational" themes related to overcoming obstacles and striving for the American Dream, Castro said. His identical twin brother, Joaquin, however, chimed in and joked that doesn't include his introduction. Joaquin is a politician in his own right - currently running for the House of Representatives in a contest Democratic leaders expect him to win.

Furthermore, Castro will elaborate on his experience as a mayor in Texas and will attempt to draw contrasts between President Barack Obama and GOP nominee Mitt Romney.

A source familiar with the speech set the bar high, saying it was akin to Obama's keynote speech in 2004 that catapulted him to political stardom.

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